1. Field of the Invention
The present invention relates to a disk discriminating method and a disk discriminating apparatus, which are capable of discriminating the kind of an optical disk.
2. Description of the Related Art
A process of discriminating the kind of an optical disk in a conventional optical disk reproducing apparatus will be described with reference to a flow chart of FIG. 9. First, the conventional optical disk reproducing apparatus initializes a gain set value temporarily stored in a work area, such as a memory, and a CD-RW decision counter (Step 81). Next, the optical disk reproducing apparatus once moves a pickup to the innermost circle of the optical disk using a tracking actuator and detects arrival of the pickup to the innermost circle, and then again moves the pickup to a signal recording part of the disk, which is near the innermost circle (Step 82). Thereafter, the optical disk reproducing apparatus irradiates the optical disk with a laser beam emitted from a laser emitting device provided in the pickup (Step 83). Next, the optical disk reproducing apparatus outputs a focus signal for disturbance, which is used to move the optical disk vertically, to a focus actuator, and generates a focus error signal, which indicates an out-of-focus, from reflected light obtained by light receiving elements of the pickup.
The conventional optical disk reproducing apparatus monitors the generated focus error signal and measures its amplitude from its maximum and minimum values (Step 84), and then compares a threshold value for the focus error signal with the amplitude to determine whether or not a focus gain is required to be changed (Step 85). If it is determined that the focus gain is required to be changed (YES in Step 85), the optical disk reproducing apparatus changes the focus gain (Step 86) and performs Step 87. On the other hand, if it is determined that the focus gain is not required to be changed (NO in Step 85), the optical disk reproducing apparatus set a tracking gain temporarily (Step 87). Thereafter, the optical disk reproducing apparatus switches on a focus servo (Step 88), accelerates rotation of the optical disk (Step 89), and sets a spindle servo to an ON state when acceleration time elapses sufficiently (Step 90).
After setting the spindle servo to the ON state, the conventional optical disk reproducing apparatus outputs a tracking signal for disturbance, which is used to move the optical disk in a radial direction, to a tracking actuator. Thereafter, the optical disk reproducing apparatus generates a tracking error signal from the reflected light obtained by the light receiving elements of the pickup, monitors the generated tracking error signal, and measures its amplitude from its maximum and minimum values (Step 91). Next, the optical disk reproducing apparatus compares a threshold value for the tracking error signal with the measured amplitude to determine whether or not a tracking gain is required to be changed (Step 92). If it is determined that the tracking gain is required to be changed (YES in Step 92), the optical disk reproducing apparatus changes the tracking gain (Step 93) and performs Step 94. On the other hand, if it is determined that the tracking gain is not required to be changed (NO in Step 92), the optical disk reproducing apparatus determines whether the optical disk is a CD-DA or a CD-RW, from set values of the focus gain and the tracking gain (Step 94).
If it is determined that the optical disk is the CD-RW (CD-RW in Step 94), the conventional optical disk reproducing apparatus adds 1 to a counter value N, and then determines whether or not the counter value N is less than a counter threshold value (3) (Step 95). If it is determined that the counter value N is less than the counter threshold value (3) (YES in Step 95), the optical disk reproducing apparatus performs Step 82 to continue the above-described processes. On the other hand, if it is determined that the counter value N is more than the counter threshold value (3) (NO in Step 95), the optical disk reproducing apparatus performs Step 96. If it is determined at Step 94 that the optical disk is the CD-DA (CD-DA in Step 94), the optical disk reproducing apparatus sets a tracking servo to an ON state (Step 96), and then performs a normal reproduction process and terminates the above-described disk discrimination process.
In brief, in the conventional disk discrimination method, when the CD-RW disk is reproduced, the processes of Step 82 to Step 95 are performed by the number of times of counter threshold values in order to increase decision precision by preventing decision miss due to low local reflection locations of the disk.
As described above, in the conventional optical disk reproducing apparatus, since a series of operations is required in order to set the gain of the focus error signal and the gain of the tracking error signal for the optical disk discrimination process performed when information recorded on the optical disk is read, it takes a long time to discriminate the kind of the optical disk. As a result, sound output from a CD player may be started late.